How should we complete and straighten the rows while performing a congregational prayer?

Where should we stand while starting a row in a congregational prayer? What is the proper way to complete and straighten the rows?

Answer:

Let the imam stand in the middle

Narrated Abu Hurairah:

"Let the Imam stand in the middle (so that those praying behind him should be standing both on his right and his left) and close the gaps.'' (Abu Dawud)

The Sunnah for the imam is to stand in line with the middle of the row, so the row should start from right behind the imam, and then be completed first to his right and to his left. It does not matter if there are slightly more people on the right than on the left. Moreover, as stated by the scholars, he who will stand right behind the imam should be a person that has enough knowledge to be imam (in order to go on salah as imam in case that the imam has any problems and have to leave the salah).

Narrated Aishah :

"Allah and His angels invoke blessings upon those who are on the right side of the rows.'' (Abu Dawud, Salât, 95; Ibni Majah, Iqamah, 55)

While joining a congregational prayer, the first rows should be filled at first

To fill the first rows means not to start a new row unless the gaps in the front one are filled.

Narrated Abu Umamah :

"Complete the front row, then the ones after it, and if there is any incompletion, it should be in the last row." (Abu Dawud, Salat,93; Nasai, Imamat, 30; Baihaqi)

Jabir ibn Samurah said:

"The Prophet (pbuh) came to us and said: 'Why don't you make the rows like the angels make their rows in the presence of their Lord?' We asked: 'O Messenger of Allah, how do the angels make their rows in the presence of their Lord?' He replied; 'they complete the first row and stand closely together, side by side, in the row.'" (Bukhari, Tirmidhi)

The importance of straightening the rows

Related Anas:

"The Prophet (pbuh) would turn his face to us before he began the salah and he would say: 'Be close together and straighten your rows.'" (Bukhari , Muslim). He also reported that the Prophet (pbuh) would say: "Make your rows straight for the straightening of the rows is part of the completion of the salah." (Bukhari , Muslim, Ebû Dâvud, Nasâî)

“The Messenger of Allah (pbuh) said, "Arrange the rows in order, stand shoulder to shoulder, close the gaps, be accommodating to your brothers, and do not leave gaps for Satan. Whoever joins up a row, he will be joined to Allah (i.e., to the Mercy of Allah); and whoever cuts off a row, he will be cut off from Allah (i.e., from His Mercy).'' (Abu Dawud)

Straightening the rows requires straightening it with the alignment of heels